Differential Amplifier question. Does the body effect change the small signal gain?

Discussion in 'Homework Help' started by hrstar24, Dec 13, 2010.

  1. hrstar24

    Thread Starter Active Member

    Apr 7, 2009
    32
    0
    So I have the following differential amplifier:

    [​IMG]

    I got 2 questions.

    1. I know the small signal gain equation for this differential amplifier if the body was connected to the source (if Vg5 is the output, excluding Q5 for now, also Q1=Q2 and Q3=Q4) is simply A = gm(ro2||ro4), but in this problem the body is connected to ground. Does that change the gain equation? If so, how?

    2. Does Q5, the common drain output buffer, change the gain also? If so, how?
     
  2. haykp

    New Member

    Oct 7, 2010
    18
    0
    First of all in real chip all the body of transistor is always connected to gnd. And I don't think that it is good to connect the body terminal of transistor to its source terminal.
    Regarding to your question then I believe if the body isnt connected to ground then it will affect on diff gain, mainly the body biasing effects of transistor will decrease.
     
  3. hrstar24

    Thread Starter Active Member

    Apr 7, 2009
    32
    0
    Thanks a lot.
     
    Last edited: Dec 13, 2010
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